Overhaul and Adjustment of Cylinder Lubrication systems
Overhaul and Adjustment of Cylinder Lubrication systems
The main purpose of the cylinder lubrication system can be summarized as below:
• Lubricate the cylinder liner surface and reduce friction between piston ring and cylinder liner by forming an oil film which will prevent wear of liner and piston rings.
• Help sealing the combustion chamber by providing gas tight seal which will improve overall engine efficiency.
• Neutralizing the acids in order to control the corrosion.
• Clean the combustion chamber and components.
In order to take advantage of the benefits explained above, which will improve the engine efficiency and reduce maintenance costs, it is very important that cylinder lubricators to be well-adjusted and functioning properly.
What will happen if cylinder lubrication systems do not function properly?
1. Excessive Lubrication (Over Lubrication):
Contrary to expectations, increasing the cylinder lubrication amount will not help to rectify the problems but will cause undesirable consequences as listed below:
• Over lubrication will result in consuming excessive oil and increasing operational costs. In many cases, saving overconsumption will cover the maintenance costs within very short periods of time.
• Generate deposits in the ring groove and prevent piston rings freely moving, which will finally cause blow-by. The phenomenon is called as hydraulic lock.
• Deposit build up on piston top land will cause mechanical bore polish and initiate the cylinder liner scuffing.
• Stopping the controlled corrosion will cause the closing of the structure of the liner surface, called chemical bore polish, and initiate liner scuffing.
• Fouling in exhaust systems and turbochargers.
2. Under Lubrication:
The target in cylinder lubrication is to minimize the cylinder oil feed rate yet maintaining acceptable cleanliness, acceptable wear and avoiding hard contact such as micro-seizures on the piston rings and cylinder liners. To avoid over-under lubrication, vessels need to optimize the cylinder lubrication feed rate through scavenge inspections and drain oil analysis.
Under lubrication may cause the below problems:
• Premature wear on the piston ring and cylinder liner due to metal contact.
• Micro seizure and hard contacts between piston ring and cylinder liner.
• Accumulated contamination from unburned fuel and combustion residues.
• Excessive corrosion.
3. Wrong Injection Timing:
Lub oil has to be injected into to cylinder at the correct timing. If system loses timing adjustments it will seriously affect the lubrication efficiency.
MECHANICALLY CONTROLLED CYLINDER LUBRICATORS:
Initially, MAN B&W engines equipped with mechanical type lubricators such as Atlas, Hans Jensen, Yasec, Yamachina. Mechanical lubricators have been serving in engines for long periods without fail, but since the new generation lubrication system called Alpha lubrication entered into service, no more mechanical type lubricators are installed on the new building engines.
Mechanical type lubricators are trouble-free and reliable lubricators, but they are driven via a gear connection to the camshaft. Therefore, normal part load control will be proportional to the speed of the engine. Because the load of the engine follows the propeller curve, i.e. the load drops three times the drop in speed, part-load oil dosages will increase significantly compared with the full-load setting. For this reason, and in order to prevent under lubrication at high load, all settings should refer to the MCR output of the engine. This is a disadvantage and weak point of the mechanically controlled lubricators because even if you adjust the feed rate to basic setting for MCR, the feed rate will be increased significantly on part loads.
Just a simple example of the disadvantage of rpm dependent lubricators; reference with service letters of MAN B&W SL12-553, basic feed rate for mechanically controlled lubricators is 1.1 g/kwh. Based on this guidance, we expected to adjust feed rate 1.1 g/kwh for MCR, but once the engine sails with lower loads such as %50 or %75, then feed rate will be increased to 1.5-1.7 g/kwh at same adjustment, because engine speed and engine load do not change at same value.
In order to correct this phenomenon, some lubricators equipped with MEP control options, also Hans Jensen made some improvements such as mechatronics or X-tronic to switch lubrication algorithms of mechanical type lubricators from speed controlled to load controlled.
Another necessity for the cylinder lubrication systems is increasing the feed rates %25 during starting, manoeuvring and load changes. There is an adjustment arm on the side of the lubricators for this purpose which need to change by ship crew during manoeuvring, while some of the lubricators do this automatically by LCD (Load Change Dependent) actuators.
It is also difficult to carry out proper pre-lubrication with mechanically controlled engines due to difficulties with application.
Disadvantages of mechanically controlled lubricators ended with the Alpha lubrication system. Alpha lub systems electronically controlled and load dependent lubricators which obtain a constant g/kwh feed rate regardless of the engine speed, activating LCD function automatically and carrying out pre-lubrication by pushing a button only.
MECHANICALLY CONTROLLED CYLINDER LUBRICATORS
MECHANICALLY CONTROLLED CYLINDER LUBRICATOR UNDER MAINTENANCE
Common Problems Found with Mechanically Controlled Cylinder Lubricators:
• Wrong feed rate adjustments such as over, under or uneven supply.
• Excessive oil leak due to hardened seals, gaskets and O-rings.
• Maladjusted or wrong timing.
• Defective components such as heaters, couplings, adjustment bolts, alarm systems etc.
• Defective LCD actuators.
• Broken survey blocks.
As Vita Engineering, we are offering proper health check, adjustment and overhaul for the mechanically controlled cylinder lubricators worldwide, including spare part supply.
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ALPHA LUBRICATION SYSTEMS:
As mentioned above, Alpha Lub systems electronically controlled and load dependent new generation and reliable systems both installed MC-C, ME-B and ME-C engines which eliminate disadvantages of the mechanically controlled engines.
The above drawing shows typical applications of the alpha lub system for MC engines, if we explain the working principal in simplified mode:
1. The Alpha lub system has its own pump station unit, commonly consisting of a small tank with heater, two small gear pumps, suction and discharge filters, pressure adjustment valve, and non-return valve. The function of the pump station is to supply constant 45-50 bar oil pressure to the alpha lubricator and send return oil to the cooler or storage tank if oil temperature reaches a certain level.
2. The ALCU (Alpha Lubricator Control Unit) system consists of three electronic components called MCU (Master Control Unit), BCU (Back Up Control Unit), and SBU (Switch Board Unit), which control the system via received information from the encoder, load transmitter, pickup sensors, lubricators, and other relevant system components and sending 24V DC signal to the relevant lubricator to activate the lubricator.
3. Alpha lubricators are equipped with one 0.75 ltr accumulator with nitrogen pressure of 25-30 bar on the inlet side, and one 0.16 ltr accumulator on the outlet side with nitrogen pressure of 1.5 bar. There is also a 3/2 way solenoid valve for activating the lubricator and an inductive sensor for feedback purposes.
4. Controlling and parameter adjustments of the system can be done through the HMI unit located in ECR.
For the ME-B/ ME-C engines, there are only lubricator units, and they are actuated through HPS oil and controlled by ECS.
ALPHA LUBRICATOR WITH INLET AND OUTLET ACCUMULATORS
Reference to MAN B&W service letter SL2016-632/AAB, the cylinder lubricator system is to be overhauled every 5 years or 32,000 R/H to ensure optimal and trouble-free operation. This will ensure trouble-free operation and dosing of the correct lubrication amount based on the provided set point.
Lack of maintenance may result in low or missing accumulator pressure, worn solenoid valves, as well as defective non-return valves, which all may cause excessive lubrication above the set point. This can be avoided by using the recommended overhaul and maintenance strategy.
It is also very important to make sure of the correct timing, functioning, and dosing of the mechanical cylinder lubrication systems.
MAINTENANCE OF ALPHA LUB SYSTEM CONSISTS OF:
1. Checking of timing and mechanical installation of angle encoder arrangement:
• Injection takes place while the first piston ring is passing the lubricator quill level, during the piston’s upward stroke. Initial adjustments of the system are set at this angle for each individual cylinder and controlled by the encoder. However, certain cases indicate the encoder lost its position or timing adjustment is wrong, hence it is necessary to check encoder adjustment and timing parameters during health checks.
2. Checking the timing and distance of BCU pick-ups:
• There are two pick-up sensors checking and confirming NO:1 Cylinder TDC for crosschecking with the encoder. The condition of the pick-up sensors, cabling, and bracket on the flywheel should be checked during overhauls.
3. Checking and adjustment of index transmitter:
• The index transmitter senses the engine load and informs the ALCU unit, hence the system can calculate engine load and arrange injection frequency accordingly. Therefore, checking the index transmitter’s condition, adjusting zero-span parameters, and adjusting load points according to the version of MCU is very important.
4. Checking of alarms:
• Checking the active and logged alarms during maintenance is necessary to understand if any corrective action is needed.
5. Replacement and filling of N2 accumulators:
• In order to obtain stable system pressure, it is vital that all accumulators are intact, and pressures are as per spec. Accumulators should be replaced every 5 years or 32,000 RH after filling the 1.5 bar Nitrogen for small accumulators and 30 bar Nitrogen for big accumulators. In case pressure fluctuations are observed in the system, the first suspicious components are burst accumulators.
6. General visual check of the cable connections for fatigue:
• Cable insulation and proper connection are very important for proper functioning and preventing electrical noise, hence, they should be closely inspected during overhauls.
7. Check and overhaul of alpha lubricators:
• Cleaning, inspecting, and replacing the O-rings and seals should be carried out during overhauling.
8. Renew the solenoid valves:
• The condition of the solenoid valves is very important for the proper functioning of the alpha lubs, hence, they should be replaced every 5 years or 32,000 RH.
9. Renew the filters at the pump station:
• Replacing the suction filters, pressure filter, spider coupling of the supply pumps, overhauling the supply pumps, and checking the supply unit components are part of the scope of the overhaul job.
10. Complete system testing:
• Testing the system in simulation mode, checking the power supply unit, short circuit check on MCU-BCU, MCU-BCU live signal check, and solenoid valve connection test should be carried out during the overhaul job.
MCU - ALARM HANDLING AND TROUBLESHOOTING:
Alarms 1-24 Feedback failure
If for any reason a feedback signal from a lubricator is measured as abnormal by the MCU, a feedback alarm will be given. A common alarm will trigger the AMS system (engine alarm and monitoring system) and an alarm code will be stored in the HMI panel. If the alarm stated in the HMI panel is a logged alarm (the alarm has disappeared again), the alarm will be displayed as LAL XX. The alarm code in the HMI panel provides information about which lubricator is suspected to fail. (Alr 2 in the HMI panel indicates that lubricator 2 on cylinder 1 is failing.) Note that in the case of one lubricator per cylinder (engine with a bore below 600 mm), the alarm will only read uneven numbers e.g. 1, 3, 5, 7 for cylinders 1, 2, 3, 4.
In the event of feedback failure, check as follows:
First, check the feedback indicator light on the intermediate box.
If the feedback indicator light is continually on, the lubricator might be sticking in a position where the feedback sensor gives a signal all the time, or the feedback sensor is defective.
To verify that the problem is in the lubricator, disconnect the plug for the lubricator and observe the indicator light on the intermediate box. If the light turns off after the plug is removed, the problem is located in the lubricator.
The lubricator must be replaced and overhauled. Alternatively, if the light in the intermediate box remains lit after the plug to the lubricator has been removed, the fault is not in the lubricator. Check the cable and plugs from the intermediate box to the lubricator for shorts. The intermediate PCB might also be suspected.
If the feedback indicator light is continually off, start by checking if the red light in the lubricator solenoid plug flashes.
Note that in the event of a feedback failure, the remaining working lubricator is running a double feed rate, and the defective lubricator is checked by the MCU by activating once every ten lubricator strokes to determine if the lubricator is still failing (for engines with two lubricators per cylinder).
If no light flashes in the solenoid plug, remove the plug from the solenoid and check again if the light starts flashing. If yes, the solenoid's coil may have an internal short, which can be confirmed by measuring the coil resistance. The normal resistance is 15 to 22 ohms for a new solenoid. If the red light flashes in the solenoid plug, but no feedback is observed, check the connections in the lubricator plugs, mounted on the cable from the intermediate box, for loose connections or shorts.
If connections in the plug are OK, the lubricator must be replaced and overhauled. If the light in the lubricator plug flashes (once every ten lubricator strokes), the lubricator is working well, but the feedback signals are not detected by the MCU. Replace the intermediate box PCB (Printed Circuit Board). If the fault is still present, check the cable to the ALCU box.
Alarm 29 Marker signal failure from encoder:
The marker signal (one pulse per revolution) is abnormal. The system will change to random lubrication based on the remaining good signals. First, check the electrical connections in the encoder terminal box as well as the connections to the ALCU control box. If no problems are found in the wiring or fuse, replace the encoder.
Alarm 30 BCU pick up 1 failure, Alarm 43 BCU pick up 2 failure:
The two marker pickups mounted on the flywheel side of the engine give one pulse every engine revolution. These signals are used by the BCU system to determine the engine speed. The signals are also used by the MCU system to monitor the signals and release an alarm in case of signal failure. Alarm number 30 indicates that BCU pickup #1 is abnormal, and alarm number 43 indicates that BCU pickup #2 is abnormal. If the Alpha lubricator system is running in BCU mode due to an MCU unit failure, the alarms for pickup failure can be found by observing the LED on the BCU PCB.
The BCU system can be operated with only one pickup signal present. Failure of one sensor is not critical and can be replaced when convenient. The BCU pickups have a built-in indicator lamp which will flash once every engine revolution. In case one of the pickup alarms is observed, first check that the light flashes in the pickup. If not, check that there is 24 volts at terminals 1, 2, and 4-5 in the BCU terminal box. If power is present at terminals 1 and 2, disconnect the sensor wire connected to terminal #3 (sensor #1) or terminal #6 (sensor #2) and observe if the light starts flashing. If yes, the wiring from the sensor to the ALCU box is shorted. If the indicator light still does not flash, replace the pickup.
Alarm 31 Trigger signal failure from encoder:
The trigger signals (1024 pulses per revolution) are abnormal. The system will change to random lubrication based on the remaining good signals. First check for loose connections and shorts in the encoder terminal box, as well as the wiring to the ALCU control box. If no problems are found in the wiring or fuse, replace the encoder.
Alarm 33 Engine stop signal failure:
Engine stop signal failure will be released if the engine stop signal is detected as abnormal by the MCU.
There are two cases that will trigger the stop signal alarm:
1. The engine is running above 8 r/min and the engine stop signal is present at the MCU input for more than 20 minutes. Check the engine stop signal circuit in the bridge control system.
2. The engine is stopped (detection is only active for 30 seconds after stop) but there is no engine stop signal present at the MCU input. Check the engine stop signal circuit in the bridge control system.
Alarm 34 LCD signal abnormal:
The MCU has detected that the external LCD signal has been continuously ON for more than 48 hours. Check the LCD signal and parameters in the governor system.
Alarm 35 BCU alive signal missing:
The MCU has detected that the BCU is abnormal. Start by checking if there are other alarms from the system. Power failure from the BCU will give this alarm. Check the wiring in MCU plug J52 terminal 4 and 5 as well as BCU plug J7 terminal 3 and 4 (BCU alive signal connections). The alive signal is a pulse signal with a frequency of approximately 1 Hz. An oscilloscope or a multimeter capable of measuring frequency must be used to measure this signal. If none of the above problems are found, try to interrupt the power to the BCU unit for 5 seconds. If the problem is still present, the BCU is probably damaged and must be replaced. However, the engine can be operated in MCU mode until a new BCU unit can be obtained.
Alarm 36 Astern signal abnormal:
The MCU unit has detected that the astern signal has been ON for more than 24 hours. The engine can be operated with this alarm present; however, the lubrication amount is increased. Check the astern signal circuit in the bridge control system.
Alarm 37 Prelubrication signal abnormal:
The MCU has detected that the prelubrication signal is ON and the index is higher than 80%. This fault is not critical. Check the prelubrication signal circuit.
Alarm 38 Oil temperature high:
The oil temperature has exceeded the alarm level normally adjusted to 70°C. Check the oil temperature sensor (Pt-100 type) by disconnecting the plug from the sensor and measure the sensor resistance.
Alarm 39 Oil pressure low:
The oil pressure is below the normal alarm level of 35 bar. Automatic start of the standby pump and common alarm is activated, plus alarm 49 in the HMI panel. If oil pressure is reestablished after start of the standby pump, the common alarm is not deactivated until the standby pump is manually stopped. Both pumps will run continuously due to the detected fault. This fault is cleared by manually pressing one of the PUMP buttons on the HMI panel.
Check if the pumps are running. Check for leaks in the high-pressure supply lines. Check the oil pressure sensor (4-20 mA type) by measuring the sensor current and comparing it with the pressure. If the current and pressure differ, the sensor must be replaced or calibrated.
Alarm 40 Speed deviation alarm:
The MCU has detected that one or more of the four speed measurements are abnormal. Check the alarm list in the HMI panel to see which sensor is abnormal (BCU pickups or the angle encoder) alarm 29, 30, 31, and 43 and read the chapter concerning the alarm.
Alarm 41 Index transmitter abnormal:
The index level does not correspond to the engine rpm. Fuel index is internally set to a fixed value of 100 percent due to the detected fault. The fault is cleared by activation of the engine stop signal. Check the adjustment of the index transmitter.
Alarm 42 Cable failure Index transmitter:
The index transmitter cable is interrupted, or the index transmitter is damaged. Correct the cable failure or replace the index transmitter. If the index transmitter is replaced, readjustment is needed.
Alarm 44 BCU in control:
The lubricators are running in BCU mode. Check that the mode switch is in auto position. Find the cause for the BCU takeover. If the BCU mode has been started automatically and is running without a slowdown command, the MCU system may be abnormal.
Alarm 45 & 46 Thermal overload electric motor:
Electric motor #1 or #2 is tripped by thermal overload. Check the thermal trip breaker in the pump station control box. Press the reset button on the thermal overload breaker to reactivate the pump motor and check the current at the ammeter local side.
Check that the voltage on all three phases is OK. If not, check the fuses in the feeder panel. Also verify that the motor windings are OK by measuring the resistance of the individual windings. If no electrical fault can be found, check the oil pump for mechanical damage.
Alarm 47 MCU parameter list not loaded:
This alarm indicates that the MCU computer has lost its configuration file or that it is missing. Change to forced BCU operation by using the mode switch and replace the MCU with a spare when possible.
Alarm 48 Angle deviation fail:
The angle difference between the TDC marker from the angle encoder and the TDC markers from the BCU pickups exceeds the alarm level. Check the initial adjustment of the angle encoder and adjust as necessary. The adjustment procedure. Also check the flexible coupling between the engine ne and angle encoder for good condition.
Alarm 49 Stand-by pump is running:
The stand-by pump has been activated either by the user or automatically due to a low-pressure alarm.
We are offering a Premium service in a cost-effective way for the alpha lubrication system maintenance, adjustment, troubleshooting and overhaul.
At VITA, all our work is done to the highest standard, meeting the exact OEM specification when required and backed up with the VITA warranty. Please contact VITA service team for further information.
CYLINDER LUBRICATION SYSTEMS ON SULZER RTA and WARTSILA RT-FLEX ENGINES
Sulzer RTA engines are also equipped with mechanical cylinder lubrication systems such as Roeen and Vogel (SKF), which is controlled by a flow control valve.
Different to MAN B&W engines, Sulzer RTA cylinder lubrication is not according to timing but according to internal pressure, which is called on demand lubrication system.
On Sulzer RTA cylinder lubrication systems, lubricator pumps are driven by a hydraulic motor and pump the cylinder lub oil to lubrication quills. Oil accumulates in the lubrication quill accumulators. When a piston ring crosses the quill, it causes the pressure on the air side of the non-return valve to drop, thus initiating the cylinder oil injection. The lubrication timing is adjusted by the piston ring pack itself as it crosses the quill, named on demand lubrication system.
In some designs of the CLU-3 lubrication system, there is progressive lubrication block between the lubrication pump and the quills. In a progressive system, the lubricant is supplied to a single inlet of a progressive block and is distributed volumetrically through a number of outlets due to the progressive movement of the pistons arranged in a sequence. If one of the quill or line is blocked, progressive block stop lubrication for all quills connected to the same block. Hence it is very important to immediately rectify the problem to obtain proper lubrication.
PROGRESSIVE BLOCK
Since the divider valves are in series with each other, each piston can dispense lubricant only when the previous piston has completed its delivery. Therefore, a blocked output will cause failure of operation of all progressive dividers connected to each other.
FREQUENCY CONTROLLED VOGEL LUBRICATOR
By the time, hydraulically controlled flow control valve systems were replaced by CLU-3 system which is driven by a frequency controlled electrical motor. For new generation engines, CLU-3 systems are replaced with CLU-4 and CLU-5 pulse jet lubrication which is somehow similar to alpha lubrication systems.
CLU-4 Pulse Lubrication System
1. Pulse Jet:
- Cylinder oil injection to the liner wall side
2. Pulse Feed
- Cylinder oil injection to the piston ring package and skirt.
The CLU-4 Pulse Jet Cylinder Lubrication System is based on a lubrication module with integrated electronics and newly developed lubricators. During operation, oil flows from the daily service tank to the lubricating oil filter and then to the dosage pump in the pulse lubrication module. Each of the cylinders is equipped with one pulse lubricating module and eight lubricators. The position of the working piston is continuously monitored by the crank angle sensor that is connected to the control system. At the defined position of the working piston, the dosage pump sends the oil to the lubricators where it is discharged.
The dosage pump in the pulse lubrication module is driven by the servo oil. This is a separate oil line that runs in a closed circuit. The servo oil is taken from the servo oil common rail through a pressure reducing valve.
Cylinder Oil Distribution
1) Pulse Jet: The lubricators deliver the lubricating oil as pulse jet feeding into the liner wall. From there, the lubricating oil is distributed around the circumference of the cylinder liner. The vertical oil distribution is determined by the injection timing. It is adjusted by means of the control system.
2) Pulse Feed: The lubricators deliver the lubricating oil as compact pulse feed exactly into the piston ring package 80% and the piston skirt 20%. From there, the lubricating oil is distributed around the circumference of the cylinder liner.
The feed rate is adjusted by skipping more or less unlubricated strokes, similar to Alpha lubrication systems. The injection is initiated on up-strokes only, similar to Alpha lub.
Clu-4 PULSE LUBRICATION SYSTEM LUBRICATION MODULE
We are offering a Premium service in a cost-effective way for the SULZER RTA and WARTSILA RT-FLEX lubrication system maintenance, adjustment, troubleshooting and overhaul.
